The saints are marching in. They have left their caves and rocky prominences to offer themselves on the blocks of London's bumper summer auctions of Old Master paintings in the first week of July.

It isn't easy being a saint, especially a miserable or a gory one. Although today's newly rich young suits have rediscovered Old Masters - wall-fillers for the respectable Nineties - saintly supplicants are more likely to find salvation in heaven than the saleroom.

Nobody wanted the 18th century Roman School painting of the poncey praying Saint Charles Borromeo, even at pounds 800-pounds 1,200, in Christie's South Kensington's April sale. But in the same sale, a big (66in by 97in) fleshy frolic by a follower of Rubens, Diana and Actaeon, a bathing scene showing Diana's blushing attendants covering themselves from the prurient gaze of Actaeon, fetched pounds 18,400, above the pounds 10,000-pounds 15,000 estimate.

Follower of? Not the real thing, then? Of course not. But do not let that put you off. Such works are not fakes, more like honest tributes. Although they may fetch only a tenth the price of fully attributed Old Masters, their quality can transcend the decorative. A "sub-Canaletto" (tongue-in-cheek auctioneers' jargon) of the Doge's Palace in Venice by Michele Marieschi (1710-43) - it does help the price if the follower's name is known - fetched pounds 1,541,500 at Christie's in December, a record for the artist.

Another sub-Canaletto of Venice, by an unnamed follower, is estimated at pounds 4,000-pounds 6,000 in Bonhams' July sale.

If City slickers and interior decorators spent their hols traipsing round museums in Naples, researching the 17th century paintings of Vaccaro or Stanzione of the Caravaggio School, you could expect London auction prices to reflect a more scholarly taste.

But the tired whizz-kids hole up instead in their villas in Tuscany and continue to demand easy, decorative Old Masters when they get back. Their money is as good as anybody else's. One of the primary rules of investment: buy what everybody else is buying.

Caroline Oliphant of Bonhams says: "Some people get frightened off by Old Masters. They think they are difficult and that they need to know a lot about them. But it is possible to appreciate many of them without knowing a great deal."

Fortunately, the London auction market in Old Masters is still dominated by dealers rather than private speculators.

That makes it more stable than, say, the contemporary art market. Old Masters are traditionally the market's sheet-anchor: slow to respond to market trends.

Italian black money created a small price surge three years ago, following a dignified decline in response to the crash of 1989-90. The sharper surge of the past couple of years is more probably due to new buyers, the dinky couples to be seen being shepherded round pre-sale views by auctioneers, than to outright speculators.

This summer, as last summer, the response to the surge in demand has been fat, spine-cracking auction catalogues offering plenty of pickings for bargain hunters in the pounds 4,000-pounds 6,000 price range - the popular price for followers' paintings capable of amusing your friends.

Such sudden overstocking is a familiar art-market phenomenon. It is governed by principles quite different from the incremental, day-to-day price movements of the equity or housing markets.

As soon as art prices dip, vendors tend not to consign and auctions become understocked.

As soon as prices rise, vendors tend to bung everything in - especially into the big annual summer sales. The result is glut: a buyer's market.

But this summer's proliferation of Old Masters could be your last chance to snap up nice pieces easily.

Sotheby's, which got away only 61 per cent of its big, 309-lot summer sale last year (75 per cent is considered acceptable for Old Masters) has learned the lessons of overstocking and has jettisoned 100 lots from this year's sale, leaving only 275. Those saints must be crying their eyes out.

Sotheby's Alex Bell says: "In summer, 1,000 lots or so in the pounds 4,000- pounds 6,000 price range throughout London is just too much for people to absorb, whether dealers or privates. At views, I've watched people just walking past them.

"For vendors in this price range, the summer is not as good as October or May." This is when lower-priced pictures are all there is to look at.

But Christie's South Kensington this summer is still gloriously overstocked with 510 lots. So wait until the end of the sale, when jaded dealers and privates will have spent their money and gone for a drink, then bid for the big (50in by 60in) crude but impressive capriccio of a classical palace on a lake from the circle of Giovanni Ghisolfi (est pounds 4,000-pounds 6,000), or the lubricous Young Man about to Surprise a Lady Sleeping by a Fire in an Interior (guy wants sex after returning from pub) from the circle of Francois De Troy, pounds 6,000-pounds 8,000.

Will such titillating trifles have grown in value in 10 years' time?

The alternative is to go for scholarly offerings such as Sotheby's oil sketch by the 17th-18th century Dutchman Jan Van Cleve, of the virgin and child with saints - for an altarpiece that survives in Ghent. Estimate pounds 5,000-pounds 7,000. But watch it: the Dutch will be on your tail.

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